Granular detergent compositions



UnitedSt tes Patent i r 2,846,401 1' GRANULAR DETERGENT COMPOSITIONS Thomas M; McCarthy and Arnvid s. Roald, Cincinnati,

Ohio," assignors to The Procter & Gamble Company, Cincinnati, Ohio, a corporation of Ohio No Drawing. Application June 28,1956 Serial No. 594,365 7 9 Claims. (Cl. 252-138) .The present invention relates to anionic detergent compositions which are free-flowing and resistant to caking, and more particularly to spray dried, heavy-duty,

phosphate-containing, anionic synthetic detergent compositionswhich possess improved stability; against caking,

lumping, and the development of a nonfree-flo wing character during storage under humid atmospheric conditions.

The invention, also relates to the process of producing suchdetergent compositions.

;Among the commercial heavy-duty synthetic detergent compositions wellknown in the art, are spray dried mixtures of water soluble anionic syntheticv detergents of the 1 sulfuric reaction product type with massive amounts of alkali metal tripolyphosphate. Such detergent compositions, for example, are disclosed in vdetail in U. S. Patent 2,486,922 to Strain. Particularly efiicient compositions, for example, are the spray dried products which are based on the sodium salt of alkyl sulfuric acid esters of higher alcohols obtained by the reduction of tallow and coconut oil and those which are based on sodium polypropylene phenyl sulfonate with 9-18, and preferably with 12-15 carbon atoms in the polypropylene chain, and.

mixtures thereof. In general, such compositions are commercially available in the form of solid spray dried granules whose components fall within the following percentage ranges: from about 20% to about 40% by weight ,ofactive synthetic from about 10% to about 60% by.

weightvofalkali metal phosphates, such as sodium tripolyphosphate,;. pyrophosphate and orthophosphate, the.

latter two phosphatesbeing present usually as a result of reversion of 'tripolyphosphate during spray drying, 'but sometimes being" deliberately added, from about.10% to-about-30%-by weight ofsodium sulfate, and from, about toabout 25% of miscellaneous ingredients,

whichjcan include, for example, moisture, perfume,

- carboxymethyl cellulose, coloring and fluorescent dyes,-

organic builders, sodium silicate, 'and other inorganic alkaline salts.

e The tendency humidity and high temperature, is known and numerous efforts have been made to overcome this tendency. Moisture-proof containers of special'and expensive construction to guard againstpenetration of moisture laden air have been 'sugg'e'sted. ,Specialsilicate formulas and other ma- "'For example, under storage conditions in southern V bf such detergent compositions; to cake, upon prolonged storage, particularlyin areas of'high ice of manufacture may reduce thetendency for the spray dried products to solidly cake in the carton, but they do not produce a composition which retains its free-flowing characteristic after storage for appreciable periodsof time at relative humidity and F. for example.

Under such conditions of temperature and humidity, the

detergent particles, even after water treatment to reduce the content of unhydrated inorganic'salts, have been observed to develop a tendency to hang together or"to adhere to each-other or to bridge or lump and, in general, to'show a reluctance to flow freely as distinguished from the freshly produced granules. I

In the course of the investigation of this problem,

examination of products possessing free-flow reluctance;

as above defined, has revealed that this undesirable" property is apparently caused by needle-like crystals which rapidly develop at about'75% relative humidityand-about f 90 Rand which tend to grow and radiate from the in'- dividual granules.

meshing or by actual inter granula'r crystal growth, a

plurality of granules can become physically-connected, thus affecting the free-flowing characteristics of the In the course of further study, such needle-like crystals were isolated and subjected to qualitative micro analysis. It was found that the crystals were intermediate hydrates of a mixture of trisodium and acidbsodium" product.

orthophosphates; This was later confirmed by X-ray diffraction pattern analysis. While such phosphates may j be purposely included in heavy-duty polyphosphate-c'ontaining detergent compositions of thena'tureof'those herein disclosed, more frequently they result either'from partial reversion of tripolyphosphate during the spray drying step or from hydrolysis of tripolyphosphate during storage subsequent to water or moisture treatment of the granules.

Itis an object of the present invention toprovide Y proved heavy-duty synthetic detergent compositions 'of improved free-flowing character and noncaking'propert-ies;

Another object is to provide heavy-dutyfsynthetic detergent phosphate-containing washing compositions'which have superior resistance to change in caking and freeflowing characteristics when subjected to storage for pro-'-- longed: periods of time 'at relatively high temperature and high humidity.

Another object is to provide animproved heavy-duty synthetic detergent composition which does not require expensive moisture-proof containers for storage under humid atmospheric conditions. i r

A further objectof the invention is toprovide a-process Y duty detergent compositions.

-The present invention is directed for the production of the above noted improvedheavycomprises agitating spray dried particles of heavy-duty synthetic detergent compositions 'hereinbefore referred to andzsimultaneously'applying to the surface thereof an aqueous'solution of a' sulfate of magnesium, 'zinc,"alumi-':" num, or mixtures ofsuch salts. Theamountof solution"? applied to the particles is selected so that the concentration of inorganic sulfate salt applied to the" granules. ranges from about 1% to about 10% of the'weight of the granulesitr'eated;preferably from about 2% to about 4%. The concentration of the inorganic sulfate in the solution) applied to the granules is not critical, and can be adjusted 70 coastal areas where high temperature and high humidity; prevail forextended periods of time, the'prior art methods within a range of 10% by weight to saturation, a concen tration of about 18% to 22%"by'weight being preferred,

so that the desired amount of magnesium, zinc, oralumi nurn salt, per se can be applied to the granules while-jat the same timethe moisture content of the-granules is in creased from the normal of about 5% to 10% content to 2,846,401} Patented A 8- 1 v Crystalshaving lengths up to 2 or- 3" times the granule diameter have been noted. By inter--- v e to the solution of the problem of development of free-flow reluctance. durmg lstoraget under certain 'condit'ions'of humidity and anamount within the range of about 12% to about 25%, preferably from about 14% to about 17%.

The temperature conditions under which the aqueous solution of sulfate salt is applied to the granules is not critical, but of course reasonable limits should be observed. For example, the invention'has been practiced by applying the solution to granules at ordinary room temperature from: about 70- F. to about 90 F. and at temperatures such as those occurring at the base of the conventional spray drying tower, that is, from about 160 F. to about 200 F. Higher and lower temperatures can also be used, but care should be exercised to produce a product having a moisture content within the aforementioned range. Thus, the amount of moisture evaporation that may take place during transfer or cooling. of the granules by airlift will bear consideration.

It has been noted that the application of the mag nesium, zinc, or aluminum sulfate, or mixture of such salts, in accordance with the invention not only imparts marked resistance to the development of free-flow reluctance in the granular product, but also surprisingly achieves a resistance to true caking that is far superior to that noted in products whose granules have been treated with water alone.

Investigation has indicated that the inorganic sulfate salt enters into chemical reaction with granular components at substantially the surface of the particles, thereby, for example, forming low or nonhydrating double salts with the phosphates, and especially those phosphates resulting, from the reversion or hydrolysis of tripolyphosphate, i. e., orthophosphates and pyrophosphates. Thus, the needle-like crystals of orthophosphate which lead to free-flow reluctance and hydrates of other phosphates which lead to caking are not formed when the treated product is exposed to humidity and temperature conditions conducive to the development of the undesirable characteristics herein mentioned.

Investigation has also shown that the anion of the inorganic salt is important in achieving optimum results and that the sulfates of magnesium, zinc, and aluminum are markedly superior to other soluble salts of these metals such as the chlorides and acetates, which are no more eflicient than water alone.

The specific method whereby the inorganic salt solution is applied to the spray dried granules does not constitute a part of the invention and the solutions may be applied continuously or batchwise as may be desired. In the normal operation of spray dried detergent granule pro duction, the dried and cooled granules are usually passed continuously through a rotating drum Where they are tumbled. The drum may be equipped with plates or batfies afiixed to the inner wall thereof to provide more effective tumbling. It is conventional to mix the spray dried granules in such a rotating drum apparatus with ingredients such as perfume, organic builder, or other desirable adjuncts that might be volatilized or thermally decomposed under the more elevated temperature conditions occurring within the spray-drying tower. Magnesium, zinc, or'aluminum sulfate solution designed for treatment of the spray dried particles in accordance with the present invention can be applied to the particles in such conventional rotating drums, either simultaneously or-sequentially with the application of other constituents by spray-on procedure. Other methods of application of the-solution to the granular particles are known in the art and can be employed without departing from the spirit of the invention.

The invention will be fully understood from the above description and especially when taken in conjunction with the specific examples which follow.

Example I 100 parts of spray dried detergent granules containing 28% sodium polypropylene benzene sulfonate in which the polypropylene radical averaged about 12 carbon atoms, about 19.5% sodium tripolyphosphate, and'about 13% sodium pyrophosphates, about 1.5% sodium orthophosphates, about 6% sodium silicate solids having a ratio of SiO Na O of 2: 1, about 7.2% moisture, about 2.4% ethanolamide of mixed coconut oil fatty acids, and the balance being mainly sodium sulfate with minor amounts of carboxymethyl cellulose, fluorescent dyes and perfume, were agitated in a rotating drum and sprayed with a water solution of magnesium sulfate having a concentration of approximately 20%. The amount of anhydrous magnesium sulfate applied to the granules amounted to about 2.5% and the moisture content. of the treated product was increased to about 17.3%. This product was packaged and stored under temperature and humidity conditions which were known to promote freefiow reluctance and'caking. The product was found to be resistant to the development of free-flow reluctance and even after fourteen days of storage was as free-flowing and free from caking as the initial product.

It is believed that the magnesium sulfate in the solution sprayed on the granules reacts with the pyroand orthophosphates at or near the surface of the granules to form low hydrating or nonhydrating magnesium-sodium phosphates. which indicates that the equilibrium moisture of the granules containing the sprayed-on magnesium sulfate decreases with increasing amounts of magnesium sulfate. If, in the product of this example, the magnesium sulfate did not react with any component of the granules, it would form its heptahydrate and an increase in equilibrium moisture would be expected. Thus, the product of this example and the products of the invention in general are characterized by a coating comprising hydrated double salts of the phosphates formed from sodium and from the magnesium (or zinc or aluminum) of the magnesium sulfate solution applied.

Example [I In the manner described in Example I, parts of the same spray dried detergent granules were treated with a solution of aluminum sulfate of approximately 20% concentration so as to coat the particles with about 2% anhydrous aluminum sulfate and to increase the moisture content to about 14.1%. The product so treated was packaged and stored under humidity and temperature conditions known to cause the development of freefiow reluctance and caking. The product was entirely resistant against the development of free-flow reluctance and was outstandingly resistant to caking.

A solution containing a mixture of aluminum sulfate and magnesium sulfate at about 20% concentration can also be employed in the place of the aluminum sulfate solution of Example 11 to yield a product having superior stability against caking and the development of free-flow reluctance.

Example III The process of Example II was repeated using a solution of zinc sulfate of about 20% concentration. The resulting granular product, onto which was sprayed about 2% anhydrous zinc sulfate, had a moisture content of about 14.2% and was at least equal to the product of Example II in its stability against caking and the development of free-flow reluctance during storage under relatively high temperature and high humidity conditions.

Example IV The treatment of detergent granules as specified in Example II is followed using a magnesium sulfate solution of approximately 20% concentration and a spray dried synthetic detergent composition containing about 35% sodium polypropylene benzene sulfonate in which the polypropylene radical averaged 12 carbon atoms, about 15.0% sodium tripolyphosphate, about 22% sodium pyrophosphates, about 2% sodium orthophosphates, about 6% sodium silicate solids having a sio zNa O This belief has been supported by evidenceratio of 2:1, about 8% moisture, and the balance being mainly sodium sulfate with minor amounts of carboxymethyl cellulose, fluorescent dyes, and perfume.

Treatment of the granules so as to apply thereto approximately 2% anhydrous magnesium sulfate and to increase the moisture content to about 15% renders the product especially stable against caking and the development of free-flow reluctance during storage under atmospheric conditions of high temperature and high humidity. The process of Example IV can also be applied to spray dried synthetic detergent granules which contain substantially greater amounts of sodium tripolyphosphate, such as from '1 to 1% times the amount of active synthetic' detergent and with smaller proportions of other phosphates, and the superiority of the products against the development of free-flow reluctance and caking under humid storage conditions is readily apparent.

In place of the polypropylene benzene sulfonate synthetic detergent used in the above examples, the sodium salt of the alkyl sulfuric-acid esters of higher alcohols derived by the reduction of coconut oil or tallow can be substituted in whole or in part to yield products having superior characteristics as regards caking and freedom of flow.

Having thus described'the invention, what is claimed is:

1. The process of improving the resistance to change, during storage under humid atmospheric conditions, in the free-flowing and non-caking character of freshly spray dried granulardeterg'ent compositions consisting essentially of a water soluble anionic synthetic detergent of the sulfuric reaction product type and hydratable alkali metal phosphates consisting essentially of a mixture of tripolyphosphate, pyrophosphates, and orthophosphates,

. which comprises agitating said spray dried granules and simultaneously spraying on thesurface thereof an aqueous solution containing at least one inorganic sulfate of a polyvalent metal selected from the group consisting of magnesium, zinc, and aluminum, in amount equivalent to from about 1% to about 10% of anhydrous inorganic sulfate based on the spray dried granules and sufficient to raise the moisture content of the composition to 'an amount within the range of about 12% to about 25%.

thetic detergent is, at least in substantial part, sodium polypropylene benzene sulfonate in which the polypropyl'ene radicals average about 12 carbon atoms.

3. The process of claim 1 in which the amount of in- 2. The process of claim 1 in which the anionic synorganic sulfate solution applied is equivalent to an amount of anhydrous inorganic sulfate within the range of about 2% to about 4% and is sufiicient to raise the moisture content of the granules to an amount within the range of about 14% to about 17%.

4. The process of claim 3 in which the inorganic sulfate is magnesium sulfate.

5. The process of claim 3 in which the inorganic sulfat is zinc sulfate.

6. The process of claim 3 in which the inorganic sulfate is aluminum sulfate. 1

7. The process of claim 3 in whichvthe concentration of the inorganic sulfate solution is in the range of about 18% to about 22% by weight. g

8. A spray dried heavy-duty synthetic detergent granule possessing improved resistance to change, during storage under humid atmospheric conditions, in the free-flowing and non-caking character of the freshly 'spray dried granule detergent compositions, consisting essentially from about 20% to about 40% by weight of water soluble anionic synthetic detergent of the sulfuric reaction product type, from about 10% to about by weight of alkali metal phosphates including sodium tripolyphosphate and the pyrophosphate and orthophosphate reversion products thereof, from about 12% toabout' 25% moisture, and from about 10% to about 30% by weight of sodium sulfate, said granules being characterized by a coating comprising hydrated double salts of said phosphates formed from sodium and from at least one polyvalent metal selected from the group consisting of magnesium, zinc, and aluminum, the amount of polyvalent metal present being equivalent to an amount of anhydrous sulfate of said metal within the range of about 1% to about 10%.

9. The product of claim 8 in which the amount of polyvalent metal present is equivalent to an amount of anhydrous sulfate of said metal within the range of about 2% to about 4% and in whichthe amount of moisture is within the range of about 14% to about 17%. 7'

References Cited in the file of this patent UNITED STATES 'PATENTS Great Britain July 30, 1952 

1. THE PROCESS OF IMPROVING THE RESISTANCE TO CHANGE, DURING STORAGE UNDER HUMID ATMOSPHERIC CONDITIONS, IN THE FREE-FLOWING AND NON-CAKING CHARACTER OF FRESHLY SPRAY DRIED GRANULAR DETERGENT COMPOSITIONS CONSISTILNG ESSENTIALLY OF A WATER SOLUBLE ANIONIC SYNTHETIC DETERGENT OF THE SULFURIC REACTION PRODUCT TYPE AND HYDRATABLE ALKALI METAL PHOSPHATES CONSISTING ESSENTIALLY OF A MIXTURE OF TRIPOLYPHOSPHATE, PYROPHOSPHATES, AND ORTHOPHOSPHATES, WHICH COMPRISES AGITATING SAID SPRAY DRIED GRANULES AND SIMULTANEOUSLY SPRAYING ON THE SURFACE THEREOF AN AQUEOUS SOLUTION CONTAINING AT LEAST ONE INORGANIC SULFATE OF A POLYVALENT METAL SELECTED FROM THE GROUP CONSISTING OF MAGNESIUM, ZINC, AND ALUMINUM, IN AMOUNT EQUIVALENT TO FROM ABOUT 1% TO ABOUT 10% OF ANHYDROUS INORGANIC SULFATE BASED ON THE SPRAY DRIED GRANULES AND SUFFICIENT TO RAISE THE MOISTURE CONTENT OF THE COMPOSITION TO AN AMOUNT WITHIN THE RANGE OF ABOUT 12% TO ABOUT 25%.
 8. A SPRAY DRIED HEAVY-DUTY SYNTHETIC DETERGENT GRANULE POSSESSING IMPROVED RESISTANCE TO CHANGE, DURING STORAGE UNDER HUMID ATMOSPHERIC CONDITIONS, IN THE FREE-FLOWING AND NON-CAKING CHARACTER OF THE FRESHLY SPRAY DRIED GRANULE DETERGENT COMPOSITIONS, CONSISTING ESSENTIALLY FROM ABOUT 20% TO ABOUT 40% BY WEIGHT OF WATER SOLUBLE ANIONIC SYNTHETIC DETERGENT OF THE SULFURIC REACTION PRODUCT TYPE, FROM ABOUT 10% TO ABOUT 60% BY WEIGHT OF ALKALI METAL PHOSPHATES INCLUDING SODIUM TRILPOLYPHOSPHATE AND THE PYROPHOSPHATE AND ORTHOPHOSPHATE REVERSION PRODUCTS THEREOF, FROM ABOUT 12% TO ABOUT 25% MOISTURE, AND FROM ABOUT 10% TO ABOUT 30% BY WEIGHT OF SODIUM SULFATE, SAID GRANULES BEING CHARACTERIZED BY A COATING COMPRISING HYDRATED DOUBLE SALTS OF SAID PHOSPHATES FORMED FROM SODIUM AND FROM AT LEAST ONE POLYVALENT METAL SELECTED FROM THE GROUP CONSISTING OF MAGNESIUM, ZINC, AND ALUMINUM, THE AMOUNT OF POLYVALENT METAL PRESENT BEING EQUIVALENT TO AN AMOUNT OFF ANHYDROUS SULFATE OF SAID METAL WITHIN THE RANGE OF ABOUT 1% TO ABOUT 10%. 